FD Editor’s Note: And it seems that along with “Torture” “Kill List” is now a perfectly acceptable concept. Sickening. More sickening is Obama’s justification for killing a U.S. Citizen without due process – read below.

One of a handful of Americans who have joined al Qaeda in Pakistan may soon find himself in the crosshairs of a U.S. killer drone, but officials will not say which one.

Current and former officials involved in the fight against terrorism tell ABC News the most likely candidates include fugitive al Qaeda mouthpiece Adam Yahiye Gadahn, the son of a California goat herder and under indictment for treason, and as many as three other American citizens who have taken up arms with al Qaeda in Pakistan or with affiliated groups battling U.S. forces along the border with Afghanistan.

Two unidentified men who each called themselves “Amriki” – “American” in Arabic – appeared several years ago in propaganda videos of an al Qaeda-aligned group in Pakistan. A third American, unnamed by sources but described as a mid-level al Qaeda facilitator in Pakistan, may also be among those possibly eyed for a drone strike for plotting attacks on other Americans.

A top al Qaeda external operations leader also believed to be hiding in Pakistan, Adnan Shukrijumah, grew up in New York and Florida but is a Guyanese citizen and legally only classified as a “U.S. Person.”

Since its inception on Sept. 10, 1988, al Qaeda has included Americans in its senior ranks who helped galvanize founder Osama Bin Laden’s hard line against the United States as a “crusader” nation bent on oppressing Muslims and lacking the mettle to withstand military challenges to its foreign policy.

Officials confirmed to ABC News that the Obama administration is wrestling over whether to use an armed drone to kill at least one unnamed “American citizen” allegedly aiding al Qaeda in a country which current and former counterterrorism officials said is likely Pakistan, where Bin Laden was killed by U.S. commandos in 2011. Capture by U.S. Special Operations forces would be extremely difficult there.

The White House and Office for the Director of National Intelligence each declined requests for comment by ABC News last week about the targeting of U.S. citizens with al Qaeda and the reported legal debate.

One senior official, who told ABC News that the individual under scrutiny is among a handful of known American “core” al Qaeda senior operatives in Pakistan, Syria, Somalia and possibly Yemen, added that the legalities of whether, how and who would be tasked with the targeted killing of a U.S. citizen posing a direct threat to other Americans have been resolved.

The target list has been fully vetted by administration lawyers, said knowledgeable sources, who believe there is high-level concern in the administration that one of the U.S. citizens may be collaterally killed in a strike primarily targeting a more senior al Qaeda leader. President Obama must approve any action to kill an American but incidental deaths of citizens traveling with al Qaeda targets have occurred three times in the past.

“I think what you’ve got here really is government acting as judge, jury and executioner – the CIA really acting as judge, jury, and executioner, with really no meaningful accountability either before the killings take place or after,” Jameel Jaffer, an American Civil Liberties Union legal director, told ABC News this week.

At the Pentagon late Friday, spokesman Navy Rear Adm. John Kirby wouldn’t address the specific issue of targeting American turncoats for drone strikes. But of the general vetting of those the U.S. military takes aim at with drones, Kirby said, “There’s a very robust discussion about targeting and who is a legitimate target and who is not.”

The U.S. government has killed at least four of its citizens in direct action assaults aimed at al Qaeda in recent years, according to Obama in a speech he gave last May. Only one, al Qaeda in the Arabian Peninsula external operations commander Anwar al-Awlaki, was deliberately targeted, in Yemen, by a drone strike; the others were collateral casualties in strikes targeting other al Qaeda figures.

“For the record, I do not believe it would be constitutional for the government to target and kill any U.S. citizen — with a drone, or with a shotgun — without [constitutional] due process, nor should any President deploy armed drones over U.S. soil,” Obama said in the speech last year. “But when a U.S. citizen goes abroad to wage war against America and is actively plotting to kill U.S. citizens, and when neither the United States, nor our partners are in a position to capture him before he carries out a plot, his citizenship should no more serve as a shield than a sniper shooting down on an innocent crowd should be protected from a SWAT team.”

Americans reported to have joined al Qaeda:

Adam Yahiye Gadahn (Pakistan)

At age 35, U.S.-born and California raised Muslim convert Gadahn is the only person known to have been charged with treason since the 1940s. He was recruited in Garden Grove outside Los Angeles as a teenager by the Egyptian leader of a sham charity, Hisham Diab, who was affiliated with the “Blind Sheikh” Omar Abdul Rahman, convicted for plotting to attack New York City landmarks, and Abu Zubaydah, the first al Qaeda leader captured by CIA after 9/11. Gadahn traveled to Pakistan and in 2004 appeared masked in an al Qaeda video as “Azzam the American” and threatening his homeland. He has since appeared unmasked in dozens of al Qaeda propaganda videos, notably calling on American admirers of Osama Bin Laden to carry out individual jihad inside the U.S. homeland. However, senior intelligence and counterterrorism officials have consistently said for a decade that despite his role in crafting some of Bin Laden’s past speeches and al Qaeda’s messaging, Gadahn is not an operational figure involved in planning actual attacks and many sources deny he is on a U.S. targeting list for a drone strike.

Mohammed Bayazid (Sudan)

A charismatic Syrian immigrant to the United States in his teens, Bayazid studied engineering briefly in Kansas City. Inspired by the writings of Palestinian jihadi Abdullah Azzam, the leader of the “Arab Afghans” fighting the Soviets in Afghanistan, he traveled to Pakistan in the late 1980s and fell in with Osama Bin Laden and his group of wealthy Arabs volunteering for the fight across the border, author Lawrence Wright wrote in his 2006 history, “The Looming Tower: Al Qaeda and the Road to9/11.” Bayazid was a founding member of al Qaeda but later denied allegations he was involved in such activities as attempting to procure uranium on behalf of Bin Laden to create crude nuclear weapons, according to “Jihad Joe: Americans Who Go To War In the Name of Islam” by author J.M. Berger. But Bayazid, who has in the past occasionally consented to journalists’ interviews, is said to be retired from jihad and unlikely to be atop a U.S. kill list, according to a source.

Ahmad Abousamra (Syria)

Born in France and raised in an affluent Boston neighborhood, Abousamra, 33, is a duel Syrian-American citizen and has been charged with providing material support to terrorists. Federal authorities have accused him of traveling to Yemen in 2002 and 2004 for terror training with Tarek Mehanna who was convicted on terrorism charges in 2011. Abousamra left the U.S. in 2006 and the FBI believes he is living with his wife and daughter in embattled Aleppo, Syria, where al Qaeda-linked foreign fighters at war with Syrian leader Bashar al Assad are plentiful.

Jehad Mostafa (Somalia or Yemen)

Born in Waukesha, Wisconsin, the 32-year old is under indictment in in his former hometown of San Diego since 2009 for his alleged involvement with the al Qaeda affiliate al-Shabaab in Somalia, though he may now be in Yemen. In Shabaab, Mostafa acted “as a training camp instructor and a leader of foreign fighters [and] is also skilled in the group’s media activities,” according to the State Department’s Rewards For Justice program. There has been some speculation that a masked American using the nom de guerre “Abu Abdullah al-Muhajir” photographed in Somalia in late 2011 was Mostafa. He gave a recorded speech stating that he was an emissary of al Qaeda leader Ayman al-Zawahiri to bring aid to Somali drought victims on behalf of “the martyr Bin Laden.”

Abu Ibrahim Amriki and Sayfullah al-Amriki (Pakistan)

Almost nothing is publicly known about these purported Americans who appeared in two videos posted on jihadi Internet forums four years ago. The bald-headed “Abu Ibrahim Amriki” — a nom de guerre — stood in the back of a pickup truck before a crowd of fighters in Pakistan’s tribal areas wielding an AK-47 in a 2010 video appearing to be “a leader or a popular figure,” according to the Long War Journal, which tracks militancy in the region. In late 2009, “Sayfullah al-Amriki” addressed the same group, the “German Taliban Mujahideen,” in English, saying, “We must rush to the lands of jihad. We must travel on the path of Allah. It is an obligation on us; it is not an option. You must fight.”